Following
the discovery of the Antarctic ozone hole in late 1985, governments
recognized the need for stronger measures to reduce the production
and consumption of a number of CFCs (CFC 11, 12, 113, 114, and
115) and several Halons (1211, 1301, 2402). The Montreal Protocol
on Substances that Deplete the Ozone Layer was adopted on 16
September 1987 at the Headquarters of the International Civil
Aviation Organization in Montreal. The Protocol came into force
on 1st January 1989, when it was ratified by 29 countries and
the EEC. Since then several other countries have ratified it.

The
Protocol was designed so that the phase out schedules could
be revised on the basis of periodic scientific and technological
assessments. Following such assessments, the Protocol was adjusted
to accelerate the phase out schedules. It has also been amended
to introduce other kinds of control measures and to add new
controlled substances to the list.